Continuous process for sulfurizing polybutenes

ABSTRACT

A CONTINUOUS PROCESS FOR SULFURIZING POLYBUTENES FOR USE IN METAL WORKING LUBRICANTS, AND A REACTOR FOR USE IN CARRYING OUT THE CONTINUOUS PROCESS, INCLUDING INTRODUCING MOLTEN SULFUR AND POLYBUTENES INTO AND ENCLOSED CHAMBER WHERE FLOW THERETHROUGH IS INTERCEPTED TO PROVIDE A SERIES OF REACTION ZONES, MIXING TO PROVIDE INTIMATE CONTACT IN AT LEAST EACH ZONE SITUATED IN THE INITIAL ONE THIRD OF THE CHAMBER VOLUME, RECYCLING SULFUR COLLECTING ON THE BOTTOM OF AT LEAST THE ZONES IN THE INITIAL ONE THIRD OF THE VOLUME, ALLOWING FLOW FROM ONE ZONE TO ANOTHER, MAINTAINING THE CHAMBER AT FROM 300*F. TO 400*F. AND COORDINATING THE VARIOUS FLOW RATES AND THE CHAMBER VOLUME WITH THE REACTION TEMPERATURE TO PROVIDE A PREDETERMINED CHAMBER RESIDENCE TIME.

Dec. 28, 1971 M, 1 DEN HERDER EI'AL 3,631,019

CONTINUOUS PROCESS FOR SULFURIZING POLYBUTENES Filed Oct. 17. 1968 3 Sheets-Sheet l A m.. E

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INVENTORS. 2 Marvin J. Den Herder TEMPERATURE, 1 x I0 Arf/,W a Borg A A BY ATTORNEYS United States Patent Olce ILS. Cl. 260-139 4 Claims ABSTRACT OF THE DISCLOSURE A continuous process for sulfurizing polybutenes for use in metal Working lubricants, and a reactor for use in carrying out the continuous process, including introducing molten sulfur and polybutenes into an enclosed chamber where flow therethrough is intercepted to provide a series of reaction zones, mixing to provide intimate contact in at least each zone situated in the initial one third of the chamber volume, recycling sulfur collecting on the bottom of at least the zones in the initial one third of the volume, allowing flow from one zone to another, maintaining the chamber at from 300 F. to 400 F. and coordinating the various flow rates and the chamber volume with the reaction temperature to provide a predetermined chamber residence time.

This invention relates to the sulfurization of polyolefins and, more particularly, to a continuous process for sulfurizing low molecular weight polybutenes and to reactors for carrying out such a continuous process.

Mineral lubricating oils containing sulfurized addition agents have been extensively used as metal working lubricants and especially as cutting oils. In recent years, it has been found that the mineral oil component of such lubricants contains constituents that may be toxic or carcinogenic in nature and therefor undesirable because of the potential harm that might occur when brought into contact with the human body.

The polycyclic aromatic constituents naturally present in most lubricating oils have been identified as the undesirable constituents. Accordingly, it -was necessary to remove substantially all of these constituents from the oil in order to provide a mineral lubricating oil suitable for the preparation of metal working oils and yet not harmful to the human body.

The sulfurized liquid triglycerides that were conventionally used as additives in the preparation of mineral oil-based metal working lubricants could no longer be employed due to their substantial insolubility in the mineral oils containing only minor amounts of polar aromatic constituents.

Because the use of such sulfurized materials is highly desirable to impart increased lubricity to mineral oil lubricants, considerable effort has been directed towards developing sulfurized materials that are soluble in the low aromatic content mineral oils. It has been discovered that sulfurized polybutenes having an average molecular weight of 300 or less provide particularly advantageous additions for mineral oils used in metal working fluids or lubricants. These polybutenes are a blend of many compounds and may contain minor amounts of components having a molecular weight of over 500 as well as compounds having a molecular weight of less than 100. The sulfurized polybutenes may be used directly with the mineral oils or may be combined with the previously used triglycerides to form a sulfurized product and then added to the mineral oil.

In forming these sulfurized polybutenes, molten sulfur is contacted with a liquid polybutene feed to carry out a reaction that involves from about 1 to 15 hours, depend- 3,631,019 Patented Dec. 28, 1971 ing upon the temperature employed. The shorter reaction times are achieved by the higher temperatures. During the initial stages of the reaction, it has been found that the polybutene dissolves only a portion of the molten sulfur. When the reaction is about one third to one half completed, the sulfurized polybutenes that have been formed are better solvents for the sulfur. The molten sulfur is then almost completely dissolved but will crystallize out if the temperature falls below about 200 F.

An operable reactor system must provide intimate mixing of the molten sulfur and the polybutenes in the early stages of the reaction and not permit the sulfur to crystallize out and plug any openings, lines, valves or pumps in the system. In addition, gas is generated during the reaction and thus must be properly vented. A close control of both reaction time and temperature is also required to obtain a quality sulfurized product. The reactor system must additionally permit cooling without causing serious plugging problems. The combination of these and other factors has restricted preparation of such sulfurized products to batch processes.

It is an object of the present invention to provide a reactor which permits the continuous sulfurizing of polybutenes.

A further object is to provide a reactor of the hereinbefore described type which lachieves inimate mixing without employing mechanical stirrers.

A still further object is to provide a reactor of the hereinbefore described type for continuously sulfurizing polybutenes that minimizes plugging and mixing problems caused by a two phase sulfur and polybutene system and the precipitation of molten sulfur with the attendant plugging problems.

Another object is to provide a continuous process for sulfurizing polybutenes which eliminates batch storage before purification can be carried out.

Other objects and advantages of the invention will be apparent as the following description proceeds, taken in conjunction with the accompanying drawings in which:

FIG. l is a schematic View of one embodiment of a reactor in accordance with the present invention together with equipment suitable for sulfurizing the polybutnenes and purifying the sulfurized polybutene product;

FIG. 2 is a schematic view illustrating another embodiment of the reactor of the present invention;

FIG. 3 is a schematic view of one type of baille that may be used in the embodiment of FIG. 2;

FIG. 4 is a schematic view of another type of baille that is employed in the embodiment of FIG. 2; and

FIG. 5 is a graph of the reaction time-temperature relationship for sulfurizing polybutenes.

While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by Way of example and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as expressed in the appended claims. For example, while the specification describes the continuous process and reactor of the present invention in connection with the sulfurization of certain low molecular weight polybutenes, it should be appreciated that the invention is equally applicable to the continuous forming of any sulfurizable hydrocarbon such as saturated hydrocarbons including mineral oils and unsaturated hydrocarbons and also polyglycerides such as lard oils.

In accordance with the present invention, there is provided a continuous process for sulfurizing low molecular weight polybutenes which comprises introducing Inolten sulfur and a polybutene feed preheated to a temperature in the range of from about 300 F. to 400 F. into an enclosed reaction chamber having at least one inlet and an outlet. The volume of the chamber is determined by the rates at which the molten sulfur and polybutene feed are being introduced. The molten sulfur and polybutene feed are brought into contact and passed through the reaction chamber. The ow is intercepted during its passage through the chamber to form at least three reaction zones. In at least each zone that is situated in the initial one third of the chamber volume adjacent the inlet, the molten sulfur and polybutene feed are mixed to provide intimate contact to aid the sulfurizing reaction. In at least those zones Where mixing is carried out, the molten sulfur collecting on the bottom of the zones is recycled to again bring it into contact with the polybutene feed. The gaseous portions of the polybutene feed and the reaction products formed (e.g. -H2S) are allowed to vent from the reaction zones. Flow from one mixing zone to the adjacent zone is allowed at a rate substantially equal to the feed inlet rate, The temperature of the enclosed reaction chamber is maintained within a range of from about 300 F. to about 400 F. The introduction rates of the molten sulfur and polybutene feed and the volume of the reaction chamber are coordinated with the temperature at which the reaction chamber is maintained to provide a predetermined chamber residence time for the molten sulfur and polybutene feed to maximize the amount of sulfur that is chemically combined with the polybutene yet without forming undesirable side products. Preferably, the temperature and residence time should be controlled in accordance with the relationship illustrated in FIG. 5.

In the preferred embodiment, the temperature is maintained at about 350 F. and the various parameters hereinbefore described are coordinated to provide a residence time of about one hour.

To carry out the continuous process for sulfurizing polybutenes, another feature of the present invention provides a reactor comprising an enclosed reaction chamlber, designed for horizontal flow therethrough, with at least one inlet for introducing the molten sulfur and polybutene feed into the chamber and an outlet. To intercept the ow during its passage through the chambers and to form separate reaction zones, the chamber includes at least two vertically positioned bafles. Intimate mixing of the molten sulfur with the polybutene feed and the sulfurized polybutenes being formed is provided by mixing means which cause turbulence and intimate contact in at least the reaction zones that are situated in the initial one third of the chamber volume adjacent the inlet. Because molten sulfur collects on the bottom of the chamber in the early stages of the reaction, those zones including mixing means also include recycle means to transport this molten sulfur mixed with polybutenes upwardly to cause intimate contact of sulfur with the liquid poly-- butene feed. The baffles have passage means of a predetermined size to allow ow horizontally from one zone to the adjacent zone. Vent means are provided to remove the lighter portions of the polybutene feed and gases formed during the reaction from the reaction zones. The reactor is also equipped with heating means capable of maintaining the molten sulfur and polybutenes at ternperatures in the range of from 300 F. to 400 F.

In accordance with one embodiment of the reactor of this invention, the passage means are located adjacent the bottom of the battles to allow increased Contact of the molten sulfur falling to the chamber bottom with the partially sulfurized polybutenes as they pass from one reaction zone into an adjacent zone. The passage means are positioned a suflcient height above the chamber bottom so that molten sulfur collecting on the bottom will build up a pool of sulfur for recycle yet not plug the passage means or allow excess amounts to be transported through the passages to adjacent zones. A small amount of steam is introduced to each chamber to promote mixing. In this embodiment, the number of reaction zones should be between 3 and 5. While unnecessary, it is desirable to have each zone of substantially equal volume.

In accordance with another embodiment of the reactor of the present invention, the enclosed chamber is tubular in shape and is provided with an outer shell in which steam or another heating medium maintains the temperature of the reactor contents between 300 F. and 400 F. The baffles in at least the initial one third of the reactor volume adjacent the inlet have the bottom portion liquid tight so that molten sulfur can collect for recirculation and mixing in a zone. The bottom portion should be sized to allow some excess sulfur to pass from one zone to the adjacent zone. The baffles also include a series of apertures that serve as the passage means, create turbulence to provide intimate mixing and inhibit back mixing. To allow the venting of the lighter components of the polybutene feed, the bales are provided with an aperture through which the gas can flow from one end of the reactor to the other. The reactor may be positioned at a slight acute angle with respect to the horizontal to assist in maintaining higher molten sulfur levels at the inlets of the recycle lines and passing the gaseous components through the chamber to an exit. Desirably, the reactor may be formed in two sections with the rst including from 2 to 4 zones having baffles that retain the molten precipitated sulfur and the other section being equipped with sufficient baffles to form from 4 to 8 zones. The baffles in the second section should not restrict flow in the bottom portion of the zones.

Turning to FIG. 1, there is shown one embodiment of the reactor of the present invention together with apparatus that may be used to continuously sulfurize polybutenes and form a purified product. To this end, the reactor 10 comprises an enclosed chamber 12 having inlets 14 and 16 and an outlet 18.

The polybutene feed from a source not shown desirably has an average molecular weight of 300 or less. These polybutenes may be prepared by any known polymerization techniques for polymerizing butene or isobutene feed stocks. The preferred polybutenes employed are a mixture of butene dimers, trimers, tetramers, or pentamers, i.e.-a mixture of butene polymers containing 8 to 20 carbon atoms in the polymer chain, obtained as byproduct from the polymerization of butene for the preparation of higher molecular Weight commercial polybutenes. It should be appreciated that minor amounts of compounds having carbon chains from 9 to 15 or more may also be present. The polybutenes are transported through line 20 into a conventional heater 22 for preheatng to a temperature in the range of from 300 F. to 400 F., preferably 330 F. to 350 F., and are then transported through line 24 to inlet 14. Molten sulfur from a source not shown is introduced into the chamber through line 26 and inlet 1,6.

To intercept the flow from the inlets to the outlet, there are provided vertically positioned baies 28 that divide the chamber 12 into a series of adjacent reaction zones 30, 32, 34 and 36. Mixing is obtained by introducing a small amount of steam from a source not shown through lines 40 and 42 and into the several reaction zones 30, 32, 34 and 36. Maximum mixing is caused by introducing the steam near the bottom of the zones.

Because the heavier molten sulfur collects in the bottom of the zones during the early stages of the reaction, generally the rst one third to one half, a portion of the sulfur is not dissolved and exists as a separate molten phase. To further assist in increasing contact during the early stages, recycle lines 44 and 46 are provided in zones 30 and 32, respectively, to transport sulfur 48 that has collected on the bottom upwardly and again into contact with the polybutene-rich reaction phase.

Flow from one reaction zone to an adjacent zone is allowed by passages 50. Preferably, the passages 50 are located above the bottom a sufficient distance to provide a retaining section in at least the zones including recycle lines to develop a pool of molten sulfur that assists the recycling. Blockage by sulfur when the system is cold is also prevented.

Venting ofthe lighter components of the polybutene feed and gaseous material formed from the reactor occurs through vent lines 52 that draw gas from each of the mixing zones 30, 32, 34 and 36. The several vent lines 52"may then Ibe joined to form a single vent 54. When the gaseous phase 56 of the reactor 10 is continuous as shown in FIG. 1, a single vent line could be used if desired. Because the battles 28 are not in contact with the top of the chamber 12, blockage of the passage means 50 would not stop operations since the ow would, after buildup, spill over the baille.

vThe volume of the reactor, the number of zones provided, the size of the baille passages and the feed rates of the polybutenes and molten sulfur should all be coordinated with the reaction temperature being employed to insure that the reaction product exiting the reactor has taken up close to the theoretical amount of sulfur that can be chemically combined with the particular polybutene feed being used. As one specific example, a reactor having a capacity of about 750 gallons, baffled to form four mixing zones with liquid ow passages having a 4 inch diameter, Will allow a total average residence time of about one hour when the temperature is maintained at about 350 F. A polybutene feed of 500 gallons per hour and a molten sulfur feed of about 500 pounds per hour are used. The injection of steam at from 300 F. to 380 F. can be used to aid mixing. Temperature control can be achieved by any conventional means (not shown) such as steam coils surrounding the reaction chamber.

While not forming a part of the present invention, PIG. 1 schematically illustrates apparatus that may be used to form a purified, sulfurized polybutene product. When using conventional batch processing, the reaction product exiting the reactor 10 through outlet 18 would be transported through a cooler to lower the temperature to from 220 F. to 280 F. The cooled reaction product would then be passed to a surge tank for storage of between 3 and 16 hours, depending upon the reaction product temperature. A storage time of about 3 hours is generally required when the product is at a temperature of about 280 F. while a 16 hour time is needed when the ternperature is at about 220 F.

In accordance with one feature of the present invention, the reaction product does not have to be passed through a cooler and stored for a number of hours. Rather, the impure reaction product can be d'ntectly transported to a stripper to remove the lighter components of the reaction mixture, i.e.-such as the unreacted polybutenes and undesirable reaction products such as HZS and various mercaptans, the reaction product is passed through line 58 to a stripper 60. Steam at 250 F. to 450 F. from a source not shown enters the stripper 60. through line 62 and passes countercurrently to the downwardly proceeding reaction product and is vented out of the strippers through line 64. It may be desirable to eliminate traces of water by also stripping with an inert gas such as nitrogen which enters the stripper through line 66. Additional heat for vaporization may be supplied by heater coils (not shown) in the stripper.

The stripped product is immediately cooled to minimize degradation. Thus, the stripped reaction product is passed through line 68 and is cooled to about 200 F. in cooler 70. For this and other coolers used, any known means may 'be used. For example, heat exchange by using water at ambient conditions could be employed. Alternatively, the polybutene feed could be used and this could then minimize the capacity of the preheater needed since the feed would already be partially preheated. The product is then passed through line 72 and allowed to cool to 160 F. or lower. The stream in line 72 is cooled still further to 80 F. to 110 F. in cooler 74.

To remove any sulfur that may be physically entrained in the reaction product, the product passes through line 76 and enters a crystallizer 78. In the crystallizer 78, the temperature is maintained at 70 F. to 90 F. and the reaction product is gently agitated by stirring or other means to allow the sulfur crystals to grow sufficiently to assist in removal by filtration. The product exits the crystallizer 78 through line 80 and is further cooled by a cooler 82. The product containing sulfur crystals is generally passed through line 84 and into a lter 86 such as a centrifugal filter, where the entrained sulfur crystals are removed through line 88. The filtered product is removed through line and may be run to a storage tank or other vessel.

In some situations it may be desirable to recycle the product through the crystallizer 78. It is accordingly desirable to provide a line '92 that can recycle product issuing from cooler 82 directly to the crystallizer. Recycle line 94 allows, if desired, the product from the cooler 82 to be indirectly recycled to the crystallizer by joining line 72 upstream of the crystallizer.

Turning to FIG. 2, there is shown another embodiment of a reactor of the present invention. While the reactor may be formed in a single integral section, it is preferred to employ two sections, and 122 as is illustrated. In section 120, recirculation is carried out and means are utilized to maintain pools of molten sulfur and control sulfur flow through the several reaction zones. Section 122 utilizes free flow-type baffles that prevents back mixing and assists in mixing of the reaction product as it passes from one zone to an adjacent zone.

'Section 120 of the reactor is charged with a polybutene feed from a source not shown preheated, as hercinbefore described, through line 124. Molten sulfur from a source not shown passes through line 126 and may desirably be connected to line 124 to initiate intimate mixing even before the reactants enter section 120 through inlet 128.

To serve as the initial Section of the reaction chamber, there is provided a tubular enclosed chamber 130. The desired temperature is maintained by a reactor shell 132 that surrounds chamber 130. Steam or other heat exchange iluids may be used in the shell 132.

Interruption of the flow from inlet 128 to an outlet 134 is created by a pair of baffles 136 that form three reaction zones 138, 140 and 142. As can best be seen in FIG. 3, the baffles 136 are generally circular in shape and have the bottom portion (preferably about the bottom quarter), indicated at 144, liquid tight so that molten sulfur precipitating out of solution will be contained in pools for recirculation. The baffles also contain a plurality of apertures 146 that cause turbulence and shear in the flow of the reaction product to provide mixing and also prevent back mixing. The baffles 136 are also provided with openings 148 adjacent their top portion to create a path for any gaseous components. Maintaining an upward slope of section from inlet 138 -to outlet 134 of about 3 to 5 will facilitate pooling of the molten sulfur as well as assisting gas flow.

To provide maximum mixing of the reactants, reaction zone 138 includes a recycle line 152 which transports molten sulfur from adjacent the bottom of the zone together with some partially sulfurized polybutenes to join sulfur feed line 126. Zones and 142 are provided, respectively, with recirculation lines 154 and 156 to bring the settled sulfur back into intimate contact with the polybutenes.

The partially sulfurized polybutenes exit through outlet 134 and pass through line 158 into the second section of the reactor 122, entering through inlet 160. Section 122 is similar in construction to section 120` and includes an enclosed chamber 162 with a shell 164 surrounding it to provide means for maintaining the chamber temperature at the desired level. Baffles 166 intercept `the ow through the chamber; and, as can best be seen in FIG. 4, these baffles are of the free tiow type. These include a plurality of apertures 168 to allow flow, to create turbulence and shear as the reaction product flows through the chamber and to prevent back mixing. This provides mixing and intimate contact of the sulfur and the polybutenes in the various zones 170 formed by the baffles. The baffles 166 also include openings 172 to facilitate the flow of gas through the zones and ultimately through vent 174. As was the case with the irst section of the reactor, it is desirable to provide an upward slope from inlet to outlet of 3 to 5.

The reaction product exiting through outlets 176 and 178 may then be cooled and forwarded to a stripper, such as is shown in FIG. l, for purification.

The sulfur and polybutene feed rates, the volume of the reactor and the number of zones should be coordinated with the reaction mixture as hereinbefore described. As one specific example, when the reaction temperature is about 350 F. and a residence time of about one hour is desired, section 120 should be about 15 feet long and section 122, 35 feet long, each with a diameter of about 16 inches.

A sulfur feed rate of 500 pounds/hour and a polybutene feed of 500 gallons/hour can be used. Section 120 may have three zones and section 122 eight. Back pressure control at the outlets may be set at from about 5 to 50 p.s.i.g.

Thus, as has been seen, the present invention provides a continuous process for sulfurizing polybutenes and a reactor for carrying out such a process. The present invention obviates the necessity of running an impure product through a cooler and into a surge tank where storage for several hours is required. Rather, the reaction product may be directly passed to the stripping step. This obviates the disadvantages generally associated with a batch process and achieves intimate mixing without the necessity of using mechanical stirrers. Additionally, the plugging and mixing problems caused by precipitation of sulfur have been minimized.

We claim as our invention:

1. A continuous process for sulfurizing polybutenes which comprises introducing molten sulfur and a polybutene feed preheated to a temperature in the range of from about 300 F. to 400 F. into an enclosed reaction 8 chamber having at least one inlet and an outlet, bringing the sulfur and polybutene feed together and passing them through the chamber, intercepting the ow during its passage through the chamber to form at least three reaction zones, mixing the sulfur and polybutene feed in at least each zone situated in the initial one third of the chamber volume, recycling the molten sulfur collecting at the bottom of at least the zone in the initial one third of the volume to bring the sulfur again into intimate contact with the polybutene feed, venting any gaseous portion from the reaction zones, allowing ow from one zone to an adjacent zone, maintaining the chamber within a temperature range of from about 300 F. to about 400 F. and coordinating the introduction rates of the sulfur and polybutene and the volume of the reaction chamber withv the temperature at which the chamber is maintained to provide a chamber residence time for the sulfur and polybutene flow in the range of from about 1 to about 15 hours.

2. The process of claim 1 wherein the polybutene feed is a low molecular weight polybutene feed.

3. The process of claim 2 wherein the chamber temperature is maintained at about 350 F. and the residence time is about one hour.

4. The process of claim 2 wherein the chamber residence time and the temperature at which the chamber is maintained are coordinated as set forth in FIG. 5.

References Cited UNITED STATES PATENTS 2,447,004 8/1948 Gamson 260-139 2,447,005 8/1948 Gamson 260-139 2,447,006 8/1948 Gamson 260-139 `2,569,095 9/1951 Gamson 260--139 CHARLES B. PARKER, Primary Examiner D. R. PHILLIPS, Assistant Examiner U.S. Cl. X.R. 23-284; 260-125 

